fix(plugin-msw): stop calling zero-parameter Faker factories with data by stijnvanhulle · Pull Request #837 · kubb-labs/plugins

stijnvanhulle · 2026-09-03T13:51:18Z

🎯 Changes

A response with no declared content (or a void schema) parses to a placeholder schema of type unknown. mswGenerator decided whether to wire up the Faker mock path with a raw truthy check on the schema (!!response.content?.[0]?.schema), which is true even for these placeholder schemas. That made the generated handler call a zero-parameter Faker factory with an argument (createPingResponse(data)), which fails TS2554: Expected 0 arguments, but got 1. The handler also emitted an unused Faker import and inferred an application/json Content-Type header for a response with no content.

hasResponseSchema in packages/plugin-msw/src/utils.ts already existed for exactly this purpose (used for Content-Type inference and the Response.tsx component), but excluded only void and any, not unknown. This change:

Adds unknown to the schemas hasResponseSchema treats as "no body"
Makes mswGenerator.tsx reuse hasResponseSchema instead of its own weaker check, for both the Faker mock path and the Faker import
Updates the createPetFaker snapshot, which had the same void-response bug baked in

Fixes #834

✅ Checklist

I have followed the steps in the Contributing guide.
I have tested this code locally with pnpm run test.

🚀 Release Impact

This change affects published code, and I have generated a changeset.
This change is for the docs (no release).

🤖 Generated with Claude Code

https://claude.ai/code/session_01A53QRXimcQx3YRBbdkZ3TH

Generated by Claude Code

Bodyless responses parse to a schema of type "unknown", but mswGenerator only checked schema truthiness to decide whether to wire up the Faker mock path. That made handlers call a zero-parameter Faker factory with an argument, failing TS2554, and add an unused Faker import plus an incorrect application/json Content-Type header. hasResponseSchema (already used for Content-Type inference) now also treats "unknown" as no-schema, and mswGenerator reuses it instead of its own weaker check. Fixes #834 Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01A53QRXimcQx3YRBbdkZ3TH

codesandbox · 2026-09-03T13:51:21Z

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coldtea-pr-lens · 2026-09-03T13:51:23Z

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🟢 +0 new · 🟠 ~6 changed · 🔴 -0 removed · 1 flow · 10 files · commit b370223

Architecture

6 components touched across 4 lanes.

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Inside the changed components — 1 view

Component view — MSW Generator Internals

Internal modules and JSX components within @⁠kubb/plugin-msw executing schema validation, response formatting, and Faker mock integration.

Data flow

Generating MSW handlers for bodyless operations

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Testing ＆ Mocking — 3 components

🟡 CHANGED @⁠kubb/plugin-msw

Generates Mock Service Worker (MSW) route handlers and response helpers from OpenAPI operations.

🟡 CHANGED MSW Generator

Builds MSW handler files, conditionally importing Faker mock factories only when valid success schemas exist.

packages/plugin-msw/src/generators/mswGenerator.tsx:1-96

🟡 CHANGED Schema ＆ Header Utils

Determines valid response schemas and content types, filtering out void, any, and unknown placeholder schemas.

packages/plugin-msw/src/utils.ts:1-57

Examples ＆ Suites — 3 components

🟡 CHANGED Advanced PetStore Pipeline

Advanced example containing updated MSW handler snapshots for PetStore operations.

🟡 CHANGED MSW Mocking Example

Example application verifying MSW handler output for bodyless error and status responses.

🟡 CHANGED OpenAPI 3.0 Integration Tests

Integration snapshot test suite covering MSW generation across baseURL, tag grouping, and parser variants.

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changeset-bot · 2026-09-03T13:51:24Z

🦋 Changeset detected

Latest commit: b370223

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@kubb/plugin-msw	Patch

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coderabbitai · 2026-09-03T13:51:27Z

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github-actions · 2026-09-03T13:55:15Z

Size Change: +69 B (+0.02%)

Total Size: 312 kB

📦 View Changed

Filename	Size	Change
`packages/plugin-msw/dist/index.cjs`	5.85 kB	+35 B (+0.6%)
`packages/plugin-msw/dist/index.js`	5.75 kB	+34 B (+0.59%)

ℹ️ View Unchanged

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`packages/plugin-axios/dist/index.js`	15 kB
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pkg-pr-new · 2026-09-03T13:55:17Z

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commit: b370223

The petStore fixture's 400/404/405 responses declare no content, so they hit the same bug as issue #834. Update their snapshots to drop the Content-Type header and make the data parameter optional, matching the fixed hasResponseSchema check. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01A53QRXimcQx3YRBbdkZ3TH

stijnvanhulle and others added 3 commits September 3, 2026 15:59

chore(examples): update generated files

a135eba

Merge origin/claude/github-issue-834-snt57d (auto-regenerated examples)

b370223

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fix(plugin-msw): stop calling zero-parameter Faker factories with data - #837

fix(plugin-msw): stop calling zero-parameter Faker factories with data#837
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